A semiconductor switch circuit used for a high-voltage DC circuit breaker has a plurality of semiconductor switching devices connected in series, and causes these semiconductor switching devices to perform a switching operation to thereby control a high-voltage/large-current power supply line. In order to control the conduction state of a plurality of semiconductor switching devices connected in series, it is necessary to supply, to the gate terminal of each semiconductor switching device, a gate signal generated by a gate drive circuit using the potential of the source terminal of the semiconductor switching device as a reference potential.
Japanese Patent Laying-Open No. 2000-4059 (PTD 1) discloses a configuration where a transformer having a common core and a plurality of different secondary windings generates an AC voltage in each secondary winding, converts the AC voltage to a DC voltage, and supplies the DC voltage to each gate drive circuit.
Japanese Patent Laying-Open No. 3-237813 (PTD 2) discloses a pulse generation circuit including a main capacitor, switch means made up of a plurality of field-effect transistors connected in series, a gate circuit supplying a gate signal to each field-effect transistor, and a gate power supply supplying a power supply voltage to the gate circuit. The gate power supply is made up of a DC power supply and a capacitor receiving and storing a voltage of this DC power supply provided via a diode.
Japanese Patent Laying-Open No. 2009-177951 (PTD 3) discloses a power conversion apparatus including an individual gate drive unit which is made up of gate drivers and interface circuits connected respectively to a plurality of switches with which a main circuit is configured. The individual gate drive unit does not require a dedicated power supply. Electric power is supplied to the gate drive unit from common power supplies fewer than the number of switches or from the main circuit, through one or more power supply terminals provided respectively to the interface circuits. From a signal source to each gate drive, an isolated signal is transmitted.
US2012/0299393 (PTD 4) discloses a breaker circuit breaking a current flowing through a power supply line, by means of a high-speed switch having series-connected power semiconductor switches.